Life Cycle Costing – Strong & Corrosion Resistant

How Sappi Saiccor’s Investment in 3CR12 Continues to Prove its Work

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Construction is an expensive business and when designing and costing a project there is always a degree of choosing between the performance aspect of a material and what it will take out of the initial budget. In the current economic climate it is understandable that companies looking to expand their facilities often make decisions driven by what seems to be the most cost effective solution in the short term.

But this view has a central failing, because it assumes that spending on a structure ends when the build is complete. In fact, there will always be ongoing maintenance costs and these are directly linked to choices made during the costing phase.

Selecting building materials is a decision about when to spend money. The negative financial effects of getting it wrong only become apparent over the long term.

COUNTER-INTUITIVE

lcc sep 2In South Africa, stainless steel isn’t yet seen as an obvious choice for structural projects, in part because its perceived to be expensive. That’s arguably a fair point as it costs more than galvanised steel at the time of purchase.

But the advantages of using stainless steel over other materials are significant and a growing body of evidence proves that structures built in an appropriate stainless steel grade perform better and require none to minimal maintenance, reduced downtime and significant longevity.

Ultimately stainless steel proves to be the less expensive option over “cheaper” alternatives.

TRIAL BY FIRE

Perhaps one of the best examples of the extreme hardiness and longevity of stainless steel is Sappi Saiccor’s mill in KwaZulu-Natal.

Situated 50km south of Durban on the Umkomazi river, the mill’s proximity to the ocean and the high level of humidity in the area means that the structures on site are under constant assault. The nature of the work being done is also punishing.

Sappi Saiccor takes eucalyptus hardwoods from nearby Sappi plantations and produces dissolving wood pulp, a specialised cellulose product that gets used in a wide range of industries including textiles, pharmaceuticals and food production.

Many of the processes involved are done under high temperatures and corrosive spillage is an ongoing risk that must be managed.

Structural materials are hard pressed to perform well under these conditions, which makes the excellent results seen with 3CR12 significant.

columbus stainlessMULTIPHASE APPROACH

Sappi Saiccor has used 3CR12 stainless steel in three project phases at its Umkomaas mill for a series of pipe and utility bridges. Phase 1 of the project was installed more than 3 decades ago, during 1981-82, using 3CR12 No. 1 stainless steel. It was and remains a good choice for industrial applications because of its outstanding corrosion and heat resistance.

Sappi Saiccor selected 3CR12 No. 1 again when they rolled out phase 2 in 1993.

But when phase 3 was installed in 2008, they chose to use the more cost effective 3CR12 HRA. The mill is an excellent case study for anyone
considering using stainless steel in construction, because it provides an opportunity not only to assess how 3CR12 performs over time, but also to appreciate how different finishes stack up against each other.

PERFORMANCE AND LONGEVITY

The 3CR12 used at the mill was recently inspected to assess how it is holding up. Sappi Saiccor were notably pleased with the performance of their
pipe bridge.

Three decades of wear has seen the phase 1, 3CR12 No. 1 steel reach its expected brown patina, but it shows no appreciable signs of corrosion, except in a few small areas where the passive layer was ground off by workmen preparing welds. Whereas, the 19-yearold 3CR12 No. 1 is still browning and has not yet reached its final colour, but is in a similarly excellent condition.

The phase 3 3CR12 HRA stainless steel revealed something interesting. The mill scale of the HRA finish is predictably corroding, but when flaked off, the stainless steel beneath it is in good condition, however, it has already reached the shade of brown that the 30-year-old phase 1 3CR12 No.
1 exhibits.

An issue with 3CR12 No. 1 is that it browns slowly over time, but it does so in a way that some customers find alarming. The effect isn’t uniform.
Initially brown spots appear and later streaking appears until the final brown tone is reached. The strength of the steel is never affected, but the cosmetic appearance is.

By contrast, 3CR12 HRA achieves the final brown tone very quickly. A customer that uses 3CR12 HRA can be assured of a fairly uniform appearance
in the steel throughout the life of the structure. Coupled with the lower cost of HRA compared with No. 1, 3CR12 HRA becomes a very attractive
structural component, especially considering that the work done by the Council for Scientific and Industrial Research (CSIR) indicates that both
3CR12 No. 1 and 3CR12 HRA should have approximately the same life expectancy.

LONG TERM SAVINGS

nd engineeringWhile the performance of 3CR12 stainless steel under these harsh coastal conditions has been excellent, it isn’t unexpected – the corrosion resistant
properties of this product are well known. The true value of Sappi Saiccor’s decision to use 3CR12 is best appreciated when considering the life cycle costing of the project: the key factor being the amount of maintenance required.

Any failure in a structure has associated costs that go far beyond the actual repair process. While damage to a facility is rectified, it often cannot operate, which means it  is haemorrhaging money; in labour costs while production line staff stand around, in orders that cannot be supplied and in contracts that go elsewhere. And when required maintenance doesn’t stop production (such as corrosion management or refinishing), it is expensive because of the labour required to do the work.

In the eight years since phase 3 was installed at the Umkomaas mill, no money whatsoever has had to be spent on maintenance. Because 3CR12 HRA
stainless steel has continued to perform exactly as anticipated, the facility has never had to be shut down due to 3CR12 maintenance.

If life cycle costing is the true measure of a construction material’s value, then 3CR12 stainless steel is often the answer.

STAINLESS STEEL FOR STRUCTURES

lcc sep 3Even though initial outlay may in some cases be higher, stainless steel offers a considerable cost advantage over other materials when used as a structural element.

The low-to-nonexistent maintenance costs offer significant savings over the life of the structure. The benefits of choosing to build with stainless steel don’t end with its corrosion resistance, its also has a much higher strength-to-weight ratio compared with many traditional construction materials.

This is a crucial point during cost calculations, because, depending on the application, it is possible to achieve similar load-bearing results while simultaneously using less material.

The practise of using stainless steel in structures overseas is on the rise and the performance of the 3CR12 HRA used at Sappi Saiccor’s mill is anexcellent demonstration why.

Ultimately, South African industry can only benefit by embracing this strong, versatile material.

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